tensor: add back support for constants
Support for passing np.arrays as cython args
Merge branch 'master' of http://github.com/heeres/qutip into td-array-format
Revert "tensor: add back support for constants"

This reverts commit d8bfe49a6cba76246e03ab368e77add772b6f2cd.
py3 compatibility
added wraper function for converting time-dependent operator-array format to operator-string format
updated support for array based time-dependence
do not use np.round in time-dependent str format in array wrapper
cleanup exec call
only update args_new when args is not None
added test case for array based time-dependence
added support for array based time dependence in mcsolve
fixed dimension on ndarray type in codegen
use warnings.warn instead of print
updated docstring of mesolve so that it mention new list-array format
fixed spelling errors in docstrings
pep8 fixes
pep8 compliance
pep8 compliance
merged from master